contaminated water; polluted water; dirty water
Refers to water that has been contaminated, often by industrial waste, radiation, or sewage. Commonly used in environmental and disaster contexts.
The treatment of contaminated water at the Fukushima Daiichi Nuclear Power Plant has become a major issue.
工場から汚染水が川に流れ出た。
Contaminated water flowed from the factory into the river.
汚水 is a broader term for dirty or foul water, including sewage, whereas 汚染水 specifically implies contamination by harmful substances.
Compound of 汚染 (osen, 'pollution') and 水 (sui, 'water').